Are you confused about the difference between centrifugal fans and impeller fans? Many people use these terms interchangeably, but they are actually quite different.
Not understanding the key differences can lead to choosing the wrong fan for your application, resulting in suboptimal performance, higher energy costs, and even potential equipment damage.
In this post, we’ll clarify the distinct characteristics of centrifugal and impeller fans, including their pressure capabilities, airflow direction, efficiency, noise levels, durability, cost, and typical applications.
What Is Centrifugal Fan
A centrifugal fan is a mechanical device designed to move air or other gases by utilizing centrifugal force. It consists of an impeller, which is a rotating disc with blades attached radially. As the impeller spins, it draws air into the center and accelerates it radially outward, creating a flow of air perpendicular to the shaft. The centrifugal force generated by the rotating impeller increases the kinetic energy and pressure of the air, allowing it to be discharged from the fan housing.
What Is Impeller Fan
An impeller fan, also known as an axial fan, is a type of fan that propels air or gases in a direction parallel to the shaft on which the blades rotate. It consists of a central hub with blades attached to it, resembling a propeller. As the impeller rotates, it creates a pressure difference that causes air to flow along the axis of rotation.
Difference Between Centrifugal Fan and Impeller Fan
Pressure Capability
Centrifugal fans are capable of generating higher pressures compared to impeller fans. The centrifugal force created by the rotating impeller allows centrifugal fans to overcome significant resistance to airflow, making them suitable for applications that require air to be moved through ducts, filters, or other obstructions.
Impeller fans are better suited for applications with low resistance to airflow, as they generate lower pressures.
Airflow Direction
In centrifugal fans, air enters the impeller axially and is discharged radially, perpendicular to the shaft.
Impeller fans move air in a direction parallel to the shaft, with air entering and exiting the fan along the same axis.
Air Volume
Impeller fans are generally capable of moving larger volumes of air compared to centrifugal fans of similar size. The axial flow design of impeller fans allows for a higher flow rate, making them suitable for applications that require significant air movement, such as cooling large spaces or equipment.
Centrifugal fans, while capable of moving substantial air volumes, are more focused on overcoming resistance and generating higher pressures.
Efficiency
Centrifugal fans with backward-curved or airfoil blades tend to have higher efficiencies compared to those with forward-curved blades.
Impeller fans can achieve high efficiencies when operating at their optimal design point, but their efficiency may decrease when faced with system resistance.
Noise Level
Centrifugal fans generally produce less noise compared to impeller fans of similar size and airflow capacity. The radial discharge of air in centrifugal fans allows for more effective noise attenuation through the use of scroll housings and duct silencers.
Impeller fans, with their axial flow design, can generate higher noise levels, particularly at high operating speeds.
Durability
Centrifugal fans with robust impeller designs and well-balanced components can withstand continuous operation and moderate levels of dust or debris.
Impeller fans, especially those with plastic or lightweight blades, may be more susceptible to damage from impact or excessive vibration.
Cost
Centrifugal fans with complex scroll housings and high-efficiency motors may have higher initial costs compared to impeller fans of similar airflow capacity.
Applications
Centrifugal fans are commonly used in applications that require high pressures, such as:
- HVAC systems for buildings, where air needs to be distributed through ductwork
- Industrial processes that involve moving air through filters, heat exchangers, or pollution control devices
- Dust collection systems in woodworking, metalworking, and other industries
- Combustion air supply for boilers and furnaces
Impeller fans are typically used in applications that require high airflow rates with low resistance, such as:
- Cooling systems for electronic equipment, such as computers, servers, and telecommunications devices
- Automotive engine cooling, where impeller fans are used to draw air through radiators
- Household and commercial ventilation, including exhaust fans and ceiling fans
- Air circulation in large indoor spaces, such as warehouses, factories, and agricultural facilities
